Nowadays, with the progress of photoelectric technology, the digital audio and video devices are more and more popular. In that, digital versatile disks (DVD) and video compact disks (VCD) are the necessary devices. In the current compact disk manufacturing technology, a burst cutting area (BCA) is on the central round hole of disk for recording the relative data of a compact disk and controlling the reading of a digital versatile disk.
Currently, the BCA clock for reading the BCA data in a digital versatile disk is used as reference clock for controlling the system chipset to read BCA data correctly. With reference to FIG. 1, which shows a timing of the BCA clock for reading the BCA data in the prior art. It can be appreciated from FIG. 1 that the data type of the BCA is defined as a combination of bit “1” and bit “0” with a period of T. The data reading must be performed according to the BCA clock. In FIG. 1, as the BCA data is one “0” in T1, then a pulse is generated in the corresponding BCA clock. When N is 1 (one “0”), then a pulse is generated with respect to the data type. Then, in T2, while as N is 2 (three “0” bits), three pulse signals are generated with respect to the BCA clock signal. Then, in T3, while as N is 3 (five “0” bits), five pulse signals are generated with respect to the BCA clock signal. When the system reads data, the above correct clock pulses are necessary. Those aforesaid are references of the BCA clocks generated by a system chipset in the data reading of the prior art. Those skilled in the art should understand that not all the prior art uses the same way to generate BCA clock.
However, in the current method for reading BCA data, it is possible that an error reading is generated due to defects of the compact disk. Referring to FIG. 2, it is illustrated that an abnormal signal occurs in the BCA data as a fault is generated in a working system, i.e., defects are generated in this compact disk so that pulses in the BCA clock are also incorrect. The example in FIG. 2 is referred to that of FIG. 1, in the periods of T2′ and T3′, data is incorrect read out due to faults in the pulses of the BCA so that the BCA data is also incorrect. In the periods of T2′ and T3′ having incorrect data reading, the BCA clock has a reference clock with a fixed period generated by the working system. After the succeeding BCA clock is correct, the pulses in this period will restore to a correct way for generating a reference clock to be used in the succeeding reading of the BCA data. However, due to the previous defect in the compact disk, although the generation of the BCA clock has restored to a normal condition, the reference pulse oscillation required in the succeeding reading of the BCA data is not matched to the original data number, the fault in the data reading still occurs.
In the aforesaid prior art, as defects occur so that the reading operation is abnormal, a fixed reference clock preset in the system will be generated in the BCA clock. This preset reference clock is not matched to the actual reference clock in the data reading. Therefore, when the BCA signal is restored to a normal condition, the oscillating signal from the reference clock generated by the BCA clock will generate faults in the data reading. In order that the generated BCA clock can cause the reading work to be performed effectively, after the BCA data restores to a normal condition, a preferred clock control method is necessary.